1. Field of the Invention.
This invention relates to the field of circuit board material manufacture, and in particular, to electroplated, multilayered printed circuit board materials.
2. Prior Art.
In U.S. Pat. No. 3,808,576, assigned to Ohmega Technologies, Inc., a multilayered printed circuit board material is disclosed containing an insulating material support layer having joined thereto an electrical resistance material layer which is in intimate contact with a conductive material layer. The electrical resistance material layer disclosed in that patent is electroplated nickel, and contains up to about 30 percent by weight of phosphorous. The electroplating bath for this layer as disclosed therein is a modification of the standard Watts bath wherein boric acid is replaced by mixtures of phosphorous acid and phosphoric acid. The plating bath also includes nickel sulfate and nickel chloride. Nickel sulfate and nickel chloride have been used in the plating industry for years as traditional nickel salts; with nickel sulfate being one of the most available and least expensive nickel salts and nickel chloride functioning as an anode corroder.
While use of the plating bath disclosed in the above referenced patent has produced a useful product, the resulting nickel-phosphorus electrical resistance material layer has several problems including excessive porosity and poor peel strength. In addition, it is desirable to enhance other electrical properties of the electrical resistance material layer.